A closeable spray nozzle attached to the downstream end of a garden hose is a useful tool. One particularly desirable reason to use such a nozzle is to stop the water flow from the hose without having to shut off the hose supply valve that is commonly some distance away from the downstream end of the hose. However, closing the spray nozzle causes high water pressure to build up in the hose, and thus creates several problems:                The hose can be damaged by the high pressure. Particularly if it is left exposed to the hot sun while charged with high water pressure, a hose will often swell, bulge and/or split.        High pressure in a hose causes water leaks at joints, fittings, and repaired places. Since hose fittings are subjected to damage from being dropped, stepped on, or otherwise abused in normal use, it is very common that the junction between two hoses, or the joint where a hose end fitting connects to a nozzle, is not perfectly sealed and therefore leaks water. Hose repair devices, including replacement hose end fittings and couplings for splicing two segments of hose together, are notorious for leaking. Under high pressure these leaks result in a significant amount of wasted water, and are very annoying because they spray water on people and things nearby.        A hose which is charged with high pressure becomes very rigid and tends to straighten, so it is difficult to handle and move about. Handling a charged hose can be likened to wrestling with a snake!        
Washing machines are among the most common appliances in the world, and are almost universally connected to water supplies by hoses. Hose failures are a common cause of floods that result in costly damage to homes. Most often, a hose failure is the result of containing continuous high pressure in the hose, and as the hose ages, becomes brittle, swollen or otherwise weakened it ultimately fails by splitting or separating from a hose end fitting. It is particularly catastrophic if this occurs when the homeowner is away or otherwise unaware of the problem. Interestingly, the only time that full house pressure is needed in a washing machine hose is during those few minutes in each cycle when the machine is filling; it can reasonably be asserted that 99% of the time, a typical washing machine hose is standing unnecessarily charged with high pressure that is subjecting it to stress, damage, and likelihood of failure. Many appliance manufacturers recommend that water supply valves upstream of the hoses be shut off whenever a washing machine is not in use. However, this recommendation does not appear to be regularly practiced by users; one insurance company claims that “washing machine hose failures cause about $150 million in damage to homes in the United States and Canada each year.”
Other fluid delivery systems can suffer from similar problems. In any system containing fluid under pressure, hoses, tubing and other components are stressed by high pressure, and leaks, if present, are exacerbated. It is desirable to provide a lower pressure to those components when the maximum delivery pressure is not needed. The invention disclosed here solves or mitigates these problems by providing high pressure when it is needed, by supplying lower pressure when high pressure is not needed, automatically, and in a completely novel way. Furthermore, it will be seen that the invention takes advantage of an inherent signal within a fluid system that enables selection of the desired pressure from a position a great distance downstream of the point where pressure is controlled, without the need for any extraneous mechanical, electrical, radio wave, or other signal that is not inherent in the fluid system.
Prior art includes water pressure regulators, well-known in the art, which can reduce the fluid pressure downstream of the regulator. Many homes and other buildings are equipped with a water pressure regulator to reduce the “street pressure” to a lower pressure (“house pressure”) in the water supply throughout the building. Typically however, the house pressure that is needed or desirable to supply the plumbing fixtures in a building (sinks, bathtubs, etc) is still much too high to contain in a garden hose without experiencing the problems described above. An additional, conventional water pressure regulator on the supply to a garden hose may be used to reduce the pressure in the hose even further. Pressure regulators designed specifically for attaching to a hose bib fitting to further reduce house pressure are available and well-known in the art. When such a regulator is used, and the flow of water is stopped or restricted at the delivery end of the hose, the pressure in the hose can build only to the pressure set-point of the regulator. This protects the hose and reduces the flow of water through any leak-points. But it is desirable to have house pressure available in a garden hose and at the nozzle when using the system to spray forcefully (such as when hosing off the driveway) or to deliver a lot of water (such as when watering lawns). Thus using an additional regulator to constantly reduce the water pressure supplied to a garden hose, to a pressure low enough to mitigate the above-described problems, is not desirable because this amount of pressure is insufficient for many common purposes. A conventional pressure regulator could be used to protect a washing machine hose, but again would not allow full house pressure when the washing machine was filling, resulting in an unacceptably slow filling rate.
Prior art also includes a fluid flow control apparatus for controlling and delivering fluid at a continuously variable flow rate to a hose, as described by Filonczuk in U.S. Pat. No. 6,561,481 which is incorporated here by reference. By means of an electrically operated valve located in a valve unit at the hose bib end of a hose, and controlled by a variable electrical switch located at the fluid outflow end of the hose, this device can solve some of the problems previously described. However, the Filonczuk device suffers from numerous problems and undesirable features. It requires an electrical energy source, in this case a battery. It requires electrical wire connecting between the switch and the valve apparatus to carry a control signal, the wire being contained inside the hose and exposed to water, and also subject to being twisted and bent along with the hose. Since the wire is permanently attached at both ends of the hose, the hose portion must be a part of the entire assembly. Therefore the length of the hose is fixed, and the hose portion, if damaged, cannot be easily removed or replaced. The length of the hose cannot be extended by coupling an additional length of common garden hose, because the control switch cannot be moved to the end of the additional hose. Also, water can drain from the hose when the valve is closed, and therefore the operator must wait while the hose refills upon reopening the valve by activating the nozzle switch. In the case of a garden hose pressure control, what is needed is a method and device to control the water pressure in a hose, such that pressure is controllable from the outflow end of the hose, that does not require an electrical or other non-inherent type of controlling signal between the outflow end of the hose and the hose bib end of the hose, and that can control the hose pressure such that high pressure is supplied when there is a demand for water (when the spray nozzle is open), but low pressure is maintained when there is not a demand for water (when the spray nozzle is closed).
Prior art also includes the method and apparatus of Green for monitoring fluid flow through a pipe described in U.S. Pat. No. 6,940,409 which is incorporated here by reference. An acoustic generator that is activated by fluid flow can be located far from an acoustic receiver within the fluid system, the receiver being capable of detecting the acoustic signal transmitted through the fluid in the system. By utilizing the fluid as a signal transmission means, Green is able to transmit a signal without the need for electrical wires or other extraneous signal carrying means. The pertinence of Green's invention to the present invention is only that it demonstrates the remarkable features and benefits gained by taking advantage of a property that is inherent in the system. In Green's case, however, an extraneous signal generator is needed. The present invention exploits an inherent signal in a fluid delivery system where both the generation and the transmission of the signal are inherent.